US 7699689 B2
An electrical discharge produces an acoustic impulse, and a reflection of the impulse from the upper coin in a coin stack is sensed so that the level of the coin stack can be determined from the time taken for the reflection to be received. Alternatively, or additionally, the acoustic impulse can be used to detect coin jams, the presence and/or width of a coin store, the state of a coin routing gate or the quantity of a vendible product.
1. A coin handling apparatus comprising a plurality of coin stores and a level detector for detecting a level of coins in a respective one of the stores, the level detector comprising means for determining the level from the time at which an acoustic impulse is determined to have been reflected by a surface whose location is indicative of the level, wherein the level detector further comprises means for generating an electric spark and the acoustic pulse is produced by the electric spark, the apparatus comprising a manifold for directing acoustic impulses from the electric spark generating means to the respective stores to enable detection of the levels of coins in the stores.
2. A coin handling apparatus as claimed in
This invention relates to vending machines and coin handling apparatus, such as may incorporate validators.
Certain aspects of the invention are of particular relevance to vending machines.
Vending machines typically have to been visited frequently by a routeperson to check that none of the stock items has run out. The visits need to be frequent enough to prevent stock items from running out, resulting in lost sales, but not so frequent as to result in unnecessary effort. This can be difficult to plan, especially as the rate at which items are sold can vary.
Vending machines can develop faults whereby a product which is intended to be vended becomes jammed, and therefore a customer who has paid for an item may find that he does not receive that item. To avoid this consequent loss, it is known to provide vending machines with sensors which determine whether a product has been vended as intended. It is also known to provide a sensor which detects when a product has run out, and in response thereto to inhibit further vends.
According to an aspect of the present invention, there is provided a vending machine which has means for measuring a quantity of a vendible product stored therein. Such an arrangement can be used for multiple purposes. It is possible to determine whether the quantity of the vendible product changes following an intended vend, thereby to confirm that the vend has taken place. If the sensed quantity does not change appropriately, the machine can be caused to attempt again to vend the product, in the hope of clearing a fault or jam. It is further possible to ensure that vends are inhibited if the level is determined to be zero. In a preferred aspect of the invention, however, a signal representing the sensed quantity is transmitted to a remote location, so that it is possible to determine, before a product has run out, that replenishment will soon be required, and a visit from a routeperson can than be arranged.
Although this aspect has been described in the context of measuring the quantity of products available for vending (and these products could be of any type, such as packages, cups, cans, or bulk items of liquid or granular solid), similar advantages can apply to use of the technique for measuring waste products, such as liquid overspill in a waste container, as the techniques will provide advance warning of when a routeperson is required. Another alternative is to measure the quantity of an item being vended (such as liquid in a cup), so as to obtain a more accurate vend than is achieved simply by, e.g. a timing operation.
Various techniques can be used to determine the quantity of a vendible product. However, there is one particularly preferred technique, which is relatively cheap to implement and which is suited for use with many different physical configurations. Consequently, according to a preferred embodiment of the invention, the quantity of a vendible product is determined by generating an acoustic impulse and determining the time taken for a reflection of the impulse from a surface to reach a receiver. As described below, a technique like this has previously been described (in GB-A-2190749) for measuring the quantity of coins in a storage tube. There is further explained below a particularly advantageous improvement which has been applied to the technique, and which is of benefit when used in a vending machine according to the present aspect of the invention.
Other aspects of the invention are of particular relevance to coin validators.
Coin validators commonly include many sensors, for example for detecting the properties of inserted coins, detecting the presence of coins at various locations within the coin path, detecting the level of coins within coin stores, etc. Many attempts have been made to produce sensors which are more effective, more compact and/or less expensive.
One example is shown in GB-A-2190749. The disclosed arrangement monitors the level of coins within a coin tube by directing a train of ultrasonic pulses towards the top of the stack and measuring the time between the emitted and reflected pulses. Such an arrangement has the advantage of providing an indication of the absolute level of coins, rather than merely an indication of whether or not the level has exceeded a certain threshold, as is the case with many common level sensors. However, the described arrangement suffers from a number of disadvantages. It is difficult to construct, because the ultrasonic transducer is a resonant structure and therefore produces ringing. Any damping used to reduce this ringing will also reduce the power output, leading to potential noise problems. Furthermore, if a substantial proportion of the transducer output is coupled into the surrounding structure, this can result in saturation of the receiving microphone. The transducer has to be spaced by a large distance from the stack of coins, because otherwise the microprocessor will detect the reflected pulse before it has ceased detecting the emitted pulse, so that the overall structure is large, in addition to being difficult to assemble.
It would be desirable to mitigate at least some of these problems.
It would be desirable in addition to provide simple and cost-effective techniques for detecting various aspects of the configuration of a coin validator, so that faults and jams can be sensed or avoided.
According to a further aspect of the invention, a coin handling apparatus is provided with an electric spark generator. In order to detect the location or presence of a surface, the spark generator is actuated to produce a pressure wave, and the time taken for the pressure wave to reach a receiver is detected.
In the embodiments described below, the pressure wave is reflected from the surface (assuming the latter is present) to a microphone. The sensing of the reflection by the microphone provides an indication of the presence of the surface and the transit time provides an indication of the location of the surface. The spark generates a powerful pressure wave with a very steep rise-time and a very brief duration. The steep rise time provides a very accurate result as compared with, for example, the arrangement of GB-A-2190749, in which the relatively shallow rise time means that the calculation of the surface location from the sensing of the reflected pulse will be amplitude dependent and therefore inaccurate. The short duration of the pulse allows the spark generator to be located close to the surface being detected without running the risk of the emitted pressure wave being detected contemporaneously with the reflected wave.
Other aspects of the invention are directed to the idea of using acoustic impulses for detecting the configuration of a coin validator; thus, for example, an acoustic impulse can be used to detect whether or not a coin store is present or whether or not a coin routing gate is in a predetermined position, by determining whether the reflected acoustic impulse is received within a particular time period. An acoustic impulse could also be used for detecting a dimension of a coin store (for example the width of a coin tube) by sensing how long it takes for the impulse to reach the receiver after having been reflected off a wall of the store. The presence of a jammed coin in a particular orientation will also be detected as a result of interference with the acoustic impulse. All these possibilities are made more practicable by the use of particularly short impulses, preferably less than 100 microsecond and more preferably less than 25 microseconds, such as may be generated by an electric spark.
Various embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:
Acceptable coins then enter a coin separator 110, which has a number of gates (not shown) controlled by the circuitry of the apparatus for selectively diverting the coins from a main path 112 into any of a number of further paths 114, 116, 118, 119 and 120, or allowing the coins to proceed along the path 112 to a path 122 leading to a cashbox 124. If the coins are unacceptable, instead of entering the separator 110 they are led straight to a reject slot via a path 126.
Each of the paths 114, 116, 118, 119 and 120 leads to a respective one of five coin tubes or containers 128, 130, 131, 132 and 134. Each of these containers is arranged to store a vertical stack of coins of a particular denomination. Although five containers are shown, any number may be provided.
A dispenser indicated schematically at 136 is operable to dispense coins from selected ones of the containers when change is to be given by the apparatus.
In order to detect the level of coins in the tube 2, a control circuit causes the triggering of a spark, and the time taken for the resulting acoustic impulse to be reflected off the uppermost coin in the stack 4 and travel to the microphone 10 is measured. Assuming that the time taken is t, and the speed of sound is V, then the stack height is given by S=H−Vt/2.
V=331.29×√(T/273) m/s, where T is the absolute temperature. Accurate results can be obtained by assuming an average temperature; however, in the preferred embodiment, a temperature sensor is used to provide even greater accuracy. This assumes that the height H is known to sufficient accuracy, which can be achieved either by control of manufacturing tolerances, or by an initial calibration operation in which the reflection time t is measured with the coin tube empty and then H is calculated to be equal to Vt/2.
The thyristor is triggered at regular intervals, e.g. 50 Hz, by a spark rate generator 36, which is coupled to the thyristor by an optical interface including an LED 38.
The spark rate generator 36 also has an output A which is delivered to the detection circuit shown in
The output of the microphone 10 is delivered through an amplifier 42 to a comparator 44. The comparator output rises whenever the microphone detects a sufficiently loud signal, such that the amplifier output exceeds a threshold VREF. The rising comparator output is applied, via an AND gate 46 to a stop input 48 of the counter 40. The clock input 49 of the counter 40 is coupled to a 10 MHz clock 50. Accordingly, the counter counts for the time between the spark being generated and the reflected impulse being received by the microphone 10. A processor 52 takes the output of the counter 40, and the output of a temperature sensor 54, in order to calculate the stack height S. The temperature sensor 54 could be a discrete sensor, e.g. a thermistor, or could be an output derived from a sensor used for other purposes, e.g. an electromagnetic sensor used to measure coin properties, in which case the sensor output when no coin is present could be used to indicate temperature.
Referring additionally to
In order to stop these initial pulses from interfering with the operation of the counter 40, a delay circuit 56 is provided to generate a blanking pulse shown at C in
In a modified arrangement, the circuit is operable to take two time measurements, t1 and t2, which as indicated in
Using such an arrangement, the coin level can be calculated by determining the distance L from the spark generator to the top of the coin stack and then from the top of the stack to the receiver, using the relationship: L/D=t2/t1.
This provides an accurate indication of level without requiring a temperature measurement, because temperature influences effect t1 and t2 correspondingly and therefore cancel out.
The need to know the dimension D can be avoided by appropriate calibration operations.
In the arrangements described above, instead of calculating the position of the top of the stack, the position can be determined by use of a look-up table addressed using the time measurement or measurements.
The spark generator may be continuously activated at a desired rate throughout a period when measurements are being made. In order to improve resolution, the processor 52 preferably takes a plurality of measurements from the counter 40 and averages them.
Alternatively or additionally, the spark rate generator 36 may be responsive to a signal from a validation circuit (not shown) which indicates that a coin is being routed to the coin store 2. In response to this, a first spark is generated in order to measure the level of coins in the tube and, at a predetermined delay period later, a second spark is generated to take a further measurement. These measurements are compared, and if the difference does not represent an additional thickness corresponding to a single coin, an error signal is generated. Alternatively, or additionally, measurements made before and after a coin dispensing operation could be compared. In these embodiments, the measurements are event-driven.
In a preferred version of the event-driven embodiments, the spark rate generator 36 enabled for a predetermined period each time a measurement is made. This enables a plurality of readings to be taken and averaged to form each measurement.
Experiments suggest that, assuming a coin set wherein the thinnest coin has a thickness of 1.75 mm, assuming no temperature compensation is used and there is a possible 10° C. variation in temperature, it is possible to obtain an accuracy which corresponds to half the thickness of a coin (with a level of 29 coins). However, the error is effectively eliminated by temperature compensation. In a practical arrangement, it is possible, without undue effort, to confine variations due to mechanical tolerances to 25% of the thickness of the thinnest coin. It is also found that because of the fast rise time of the acoustic impulse, it is possible to measure a reflection time to 0.1 microseconds resolution. By averaging 10 readings, it is found that a resolution equating to approximately 0.18 mm is obtained.
Accordingly, using the teachings of the invention, a measurement resolution which is better than the thickness of a single coin is readily achievable. This compares with the arrangement in GB-A-2190749, in which experiments suggest that the rise time of the acoustic impulse is likely to be of the order of 250 microseconds, and the overall time of the impulse possibly in the order of 1.5 milliseconds. Furthermore, if the transducer is damped to reduce the pulse width sufficiently, the power of the impulse is so low that noise problems present themselves. Accordingly, for practical purposes the resolution of a single coin would be very difficult, if not impossible, to achieve.
The use of the manifold 60 for conveying the acoustic impulse to respective areas has been found to reduce significantly the cost of and space occupied by the device according to the present invention. The microphones can be successively switched into and out of circuit so that the same detection arrangement can be used for all of the level sensors.
Referring again to
Preferably the mounting arrangements for the individual containers are such that the centre of the top of each container is always located at a predetermined position, irrespective of the diameter of the container. Thus, if for example the container 128 were to be replaced by a container of different diameter, as indicated at 129 in broken lines, the container, the end 66 of the manifold and the microphone 68 would still have the appropriate relative positions for correct operation.
As explained further below, it is possible to apply the techniques of the invention for detecting parameters other than the level of coins in a coin tube. It has been determined that similar techniques can be used to advantage for other purposes, and that this is made particularly practicable if it is possible to produce acoustic impulses which have a very fast rise time and short duration, because this enables the fitting of the detector into a compact coin validator. Accordingly, an electrical arc discharge arrangement such as that mentioned above is particularly desirable. However, it may be possible to use other arrangements, for example, a damped piezoelectric transducer which is energised by a brief, high voltage, although it is envisaged that this would be significantly more difficult to achieve.
Separate acoustic impulse generators may be provided for different purposes in the coin validator. However, in a particularly preferred embodiment of the invention, generated acoustic impulses are used for multiple purposes. This could be achieved by having several different microphones at predetermined positions so as to detect respective reflections from respective surfaces. Alternatively, as in the arrangement described in the following paragraph, the same generator and microphone can be used for more than one purpose, given a suitable arrangement for analysing the output of the detecting circuitry.
Referring again to
A similar effect is produced also if the coin tube 2 is not present. Accordingly, even if there is no possibility of a jam in the coin tube, the processor may be arranged to generate an error signal if no reflected impulse is sensed by the microphone within a predetermined interval following the generation of the spark.
The techniques of the invention could also be used for determining the level of coins in a cashbox, even when these are disposed in a disordered manner. In these circumstances, it may be desirable to use two or more level sensors, and/or the arrangement may be such that the sensor is intended to indicate only when the level exceeds the predetermined threshold.
It should be noted that the techniques of the invention could be used exclusively for purposes other than coin level sensing.
The machine has three pairs of acoustic impulse transmitter/receivers 8, 10 forming respective level sensors, all coupled to a central controller 514. Each is structured like the level sensor of
The level sensors are arranged to measure (a) the number of cups in the cup store 502, (b) the level of liquid dispensed into a cup 508 and (c) the level of liquid in the overspill container 512. The controller is coupled to a modem 516, which is itself connected to a socket 518 for receiving a standard telephone cable. The arrangement is such that whenever the measured level of the cups in the store 502 falls below a predetermined level, and whenever the level in the overspill container 512 exceeds a predetermined level, the controller 514 uses the modem 516 to communicate with a remote location to advise that servicing will soon be required. As an alternative, the remote location can be arranged to poll the vending machine regularly, to determine the levels in the cup store 502 and the overspill container 512.
The controller 514 is arranged to terminate the dispensing of liquid to the cup 508 if the level of the liquid therein exceeds a predetermined value.
The cups may be pre-filled with appropriate ingredients. Alternatively, there may be a separate store for the ingredients, in which case a further level sensor may be provided for this store.
It is not necessary for all these sensors to be provided. If more than one sensor is provided, it may be possible for them to use a common acoustic pulse generator 8. Although it is desirable for the sensors to use electric arc discharges to produce the acoustic impulse, this is not essential, especially if more room is available and/or less accuracy is required.
A level sensor incorporating an electric arc discharge device 8 and a receiver 10 are provided. The acoustic impulse from the arc travels along the axis of the helical structure 604, and is reflected to the receiver 10 by the last product held in the structure, so the time of receipt of the reflected impulse represents the number of products stored in the helix. This arrangement can be controlled and used as the arrangements described above.
In the arrangements of